Confirm. Here is a simplified example to reproduce.
Example
<%@ Page Language="C#" %>
<%@ Register Assembly="Ext.Net" Namespace="Ext.Net" TagPrefix="ext" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Ext.NET Example</title>
<ext:ResourcePlaceHolder runat="server" Mode="ScriptFiles" />
<script type="text/javascript" src="resources/js/ColumnHeaderGroup.js"></script>
</head>
<body>
<ext:ResourceManager runat="server" />
<ext:GridPanel ID="GridPanel1" runat="server" Height="340">
<Store>
<ext:Store runat="server" />
</Store>
<View>
<ext:GridView runat="server" ForceFit="true">
<HeaderGroupRows>
<ext:HeaderGroupRow>
<Columns>
<ext:HeaderGroupColumn Header="Group" ColSpan="1" />
<ext:HeaderGroupColumn Header="Group" ColSpan="2" />
<ext:HeaderGroupColumn Header="Group" ColSpan="2" />
<ext:HeaderGroupColumn Header="Group" ColSpan="2" />
<ext:HeaderGroupColumn Header="Group" ColSpan="2" />
<ext:HeaderGroupColumn Header="Group" ColSpan="2" />
<ext:HeaderGroupColumn Header="Group" ColSpan="1" />
<ext:HeaderGroupColumn Header="Group" ColSpan="6" />
</Columns>
</ext:HeaderGroupRow>
</HeaderGroupRows>
</ext:GridView>
</View>
<ColumnModel>
<Columns>
<ext:Column Header="1" DataIndex="test" />
<ext:Column Header="2" DataIndex="test" />
<ext:Column Header="3" DataIndex="test" />
<ext:Column Header="4" DataIndex="test" />
<ext:Column Header="5" DataIndex="test" />
<ext:Column Header="6" DataIndex="test" />
<ext:Column Header="7" DataIndex="test" />
<ext:Column Header="8" DataIndex="test" />
<ext:Column Header="9" DataIndex="test" />
<ext:Column Header="10" DataIndex="test" />
<ext:Column Header="11" DataIndex="test" />
<ext:Column Header="12" DataIndex="test" />
<ext:Column Header="13" DataIndex="test" />
<ext:Column Header="14" DataIndex="test" />
<ext:Column Header="15" DataIndex="test" />
<ext:Column Header="16" DataIndex="test" />
<ext:Column Header="17" DataIndex="test" />
<ext:Column Header="18" DataIndex="test" />
</Columns>
</ColumnModel>
</ext:GridPanel>
</body>
</html>
The fix has been committed to SVN, revision #4197.
The fix will also appear in v1.6.
Here is the fix to add into the page <head>.
Fix
<ext:ResourcePlaceHolder runat="server" Mode="ScriptFiles" />
<script type="text/javascript">
Ext.ux.grid.ColumnHeaderGroup.prototype.getGroupStyle = function (group, gcol) {
var width = 0, hidden = true;
for (var i = gcol, len = gcol + group.colspan; i < len; i++) {
if (!this.cm.isHidden(i)) {
var cw = this.cm.getColumnWidth(i);
if (typeof cw == 'number') {
width += cw;
}
hidden = false;
}
}
return {
width: (Ext.isBorderBox || (Ext.isWebKit && !Ext.isSafari2 && !Ext.isChrome) ? width : Math.max(width - this.borderWidth, 0)) + 'px',
hidden: hidden
};
}
</script>
Thanks for the report!